Oscillatorless dc-dc power converter

ABSTRACT

A power converter for coupling an energy source to a load device comprising a selectively coupled output stage to deliver energy from an energy source to a load device, a controller coupled to the output stage, an output stage, a capacitive element coupled to the output terminals, a rectifying element, and a switch responsive to a control signal from the controller. The rectifying element and switch are coupled to the inductive and capacitive elements. The controller is responsive to input signals for generating the control signal to open the switch in a first state and close the switch in a second state. The input signals to the controller produce one or more output voltages across the output terminals, an input voltage across the input terminals, a selectable reference voltage and a feedback signal measured with respect to the inductive element.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of, and hereby incorporatesby reference in its entirety, the commonly owned U.S. ProvisionalApplication Serial No. 60/141,119, that was filed on Jun. 25, 1999 byDragan D. Nebrigic, Milan M. Jevtitch, Vig Sherill, Nick Busko, WilliamMillam and Peter Hansen: entitled “BATTERY HAVING BUILT-INDYNAMICALLY-SWITCHED CAPACITIVE POWER CONVERTER.”

[0002] This application is also related to the following co-pending andcommonly owned application which was filed on even date herewith byDragan D. Nebrigic, et. al.: U.S. Ser. No. 09/532,918 entitled“DYNAMICALLY-CONTROLLED, INTRINSICALLY REGULATED CHARGE PUMP POWERCONVERTER” (P&G Case No. 7993) and which is hereby incorporated byreference herein in its entirety.

FIELD OF THE INVENTION

[0003] The present invention relates to DC/DC power supply controllers,and more particularly to regulated inductive power converters forintegrated power management systems.

BACKGROUND OF THE INVENTION

[0004] Advances in electronics technology have enabled the design andcost-effective fabrication of portable electronic devices. Thus, usageof portable electronic devices continues to increase as do the numberand types of products. Examples of the broad spectrum of portableelectronic devices include pagers, cellular telephones, music players,calculators, laptop computers, and personal digital assistants, as wellas others.

[0005] The electronics in a portable electronic device generally requiredirect current (DC) electrical power. Typically, one or more batteriesare used as an energy source to provide this DC electrical power.Ideally, the energy source would be perfectly matched to the energyrequirements of the portable electronic device. However, most often thevoltage and current from the batteries are unsuitable for directlypowering the electronics of the portable electronic device. For example,the voltage level determined from the batteries may differ from thevoltage level required by the device electronically. In addition, someportions of the electronics may operate at a different voltage levelthan other portions, thereby requiring different energy source voltagelevels. Still further, batteries are often unable to respond quickly torapid fluctuations in current demand by a device.

[0006] A typical arrangement is shown in FIG. 1 for a portableelectronic device 10 that includes an energy source 12, such as one ormore batteries, and a load device 14, such as the internal electronicsthat require electrical power. Interposed between the energy source 12and the load device 14 is a power supply 16 that may perform a number offunctions. For example, a power converter 20, depicted as integral tothe power supply 16, provides the necessary changes to the power fromthe energy source 12 to make it suitable for the load device 14.

[0007] The power supply 16 may also perform functions other than powerconversion. For example, protecting the energy source 12, load device 14and/or power converter 20 from damage by a sustained high electricalcurrent may require electrically disconnecting the energy source 12 fromthe rest of the portable electronic device 10. As another example, thepower converter 20 may require assistance during start-up which isprovided by the supply 16.

[0008] With respect to the types of power conversion required, the powerconverter 20 may “step up” (i.e., boost) or “step down” the voltage.That is, the converter 20 may increase or decrease the input voltageV_(S) from the energy source 12 across a pair of input terminals 24, 25to an output voltage V_(O) provided to the load device 14 across a pairof output terminals 26, 27. The power converter 20 may also store anamount of energy to satisfy a brief spike or increase in demand by theload device 14 that the energy source 12 is unable to provide.

[0009] The power converter 20 may also regulate the output voltageV_(O), keeping it close to the desired output voltage level and reducingrapid fluctuations that may cause detrimental noise or cause undesirableperformance of the load device 14. Such fluctuations may occur due tochanges in demand by the load, induced noise from externalelectromagnetic sources, characteristics of the energy source 12, and/ornoise from other components in the power supply 16.

[0010] Inductive DC-DC power converters are often used in medium tomedium/high capacity switching power supplies. Known inductive DC-DCpower converters are based upon switching an output stage between acharge and discharge state. The output stage includes a switch that,when closed during the charge state, causes an inductive element, suchas an inductor to charge (i.e., to store energy in an electric field)from the energy source. A rectifying element, such as a diode, isnon-conductive, thereby preventing discharging to a load capacitoracross the output terminals. During the discharge state, the switch isopened and the rectifying element conducts allowing the inductor todischarge into the load capacitor.

[0011] Known inductive DC-DC power converters are configured in variousways in order to achieve greater capacities, voltage ranges, andinverting/noninverting outputs. An inverted output has the oppositealgebraic sign as the input. For example, an input voltage is providedat the positive input terminal 24 at +1.5 V referenced to a groundednegative input terminal 25. The positive output terminal 26 is groundedand the negative output terminal 27 is −1.0 V. Examples of knownconfigurations include converters referred to buck, boost, buck-boost,noninverting buck-boost, bridge, Watkins-Johnson, current fed bridge,uk, single-ended primary inductance converter (SEPIC), buck square.

[0012] Inductive DC-DC power converters are often chosen due to powerefficiencies which are greater than other converters such as linearconverters, whose efficiency is related to the ratio of output voltageV_(O) to input voltage V_(S). Also, the output voltage V_(O) ofinductive converters is generally related to the duty cycle of theswitching, rather than the operating frequency of the switching, unlikegenerally known capacitive power converters.

[0013] However, known output stages for inductive DC-DC power converters20 do have some drawbacks related to the capacitor, switch, andrectifying elements used in the converter. Specifically, reliance upon adiode as the rectifying element imposes a voltage drop across the diodethat makes low input voltages (e.g., sub-one volt) impractical. Inaddition, generally known switches similarly require a control signal ofa magnitude unsuitable for low input voltages. In addition, the range ofpractical inductance and capacitance values is constrained by achievableoperating frequencies of the controller. Therefore, relativelyexpensive, noisy, and relatively large discrete inductors are requiredfor the power output stage within an inductive converter.

[0014] Furthermore, known inductive DC-DC power converters 20 rely uponoscillator-based control. The inductor-capacitor combination chosen forthese known “oscillator-controlled power converters” 20 generallydictate an operating frequency suitable for operation. Adjustments tothe power delivered by the oscillator-controlled power converter isoften provided by Pulse Width Modulation (PWM) or Pulse FrequencyModulation (PFM) by a controller. The problems with PWM and PFM schemesinclude circuit and fabrication complexity. Such complexity results indifficulty in miniaturizing the power converter 20 due to the number ofdiscrete components necessary and/or the required area allocated on asemiconductor device.

[0015] In addition to the drawbacks associated with their complexity,oscillator-controlled power converters are also inefficient with lightloads due to the continued operation of the oscillator.

[0016] Still further drawbacks in the prior art are the result of someinductive DC-DC power converters 20 using feedback, either inductorvoltage V_(L) or inductor current i_(L), feedback to sense the energystored in the inductor as well as to sense the output voltage V_(O).These feedback techniques cause problems due to the nature of PWM andPFM control. For instance, inductor voltage V_(L) feedback is anindirect approach to sensing the stored energy in the inductor L andintroduces noise into the feedback voltage V_(F), (which is the same asor directly related to the inductor voltage V_(L),) due to fluctuationsin input voltage V_(S) and/or demand by the load device 14. Usingcurrent feedback avoids sources of voltage noise; however, knowncurrent-feedback power converters 20 suffer problems with respect toinadequate robustness to noise disturbances in the current feedbacki_(F), (which is the same as or directly related to the inductor currenti_(L),) resulting in premature switching and reduced power converterstability.

SUMMARY OF THE INVENTION

[0017] The invention overcomes the above-noted and other deficiencies ofthe prior art by providing an apparatus and method for a dynamicallycontrolled inductive DC/DC power converter that efficiently transferspower from an energy source as demanded by a load device.

[0018] In particular, in one aspect consistent with the invention, adynamic controller operates an inductive power output stage to transferenergy at a rate to maintain an output voltage V_(O) across a loadcapacitor C_(L). More particularly, a power converter has a power outputstage that is operable to electrically couple to input terminals of anenergy source input terminals and to output terminals of a load device.The power output stage includes an inductive element that is charged byan inductor current supplied by the energy source during a charge state.The power output stage also includes the load capacitor that is chargedby the inductive element during a discharge state. The dynamiccontroller is responsive to input signals for selectively andnon-oscillatorily generating the control signal S2 to open the switch ina discharge state and close the switch in the charge state. The inputsignals to the controller including one or more of an output voltageacross the output terminals, an input voltage across the inputterminals, a selectable reference voltage and a feedback voltagemeasured across the inductive element.

[0019] These and other objects and advantages of the present inventionshall be made apparent from the accompanying drawings and thedescription thereof.

BRIEF DESCRIPTION OF THE FIGURES

[0020] The accompanying drawings, which are incorporated in andconstitute a part of this specification, illustrate embodiments of theinvention, and, together with the general description of the inventiongiven above, and the detailed description of the embodiments givenbelow, serve to explain the principles of the present invention.

[0021]FIG. 1 is a top-level block diagram of a portable electronicdevice incorporating a power supply with a power converter.

[0022]FIG. 2A is a top-level diagram of an output stage for a buck powerconverter.

[0023]FIG. 2B is a top-level diagram of an output stage for a boostpower converter.

[0024]FIG. 3 is a top-level block diagram of a dynamically controlledinductive power converter in accordance with the invention.

[0025]FIG. 4 is one embodiment of a circuit for a start-stop controllerfor the boost power converter of FIG. 2B in accordance with theinvention.

[0026]FIG. 5 is an embodiment of a circuit for a voltage-feedbackoscillator-less controller for the boost power converter of FIG. 2B inaccordance with the invention.

[0027]FIG. 6 is a flow diagram for the operation of the voltage-feedbackoscillator-less controller of FIG. 5 in accordance with the invention.

[0028]FIG. 7 is an embodiment of a start-up circuit for the boost powerconverter of FIG. 5 in accordance with the invention.

[0029]FIG. 8 is a wave diagram for the start-up circuit of FIG. 7.

[0030]FIG. 9 is a flow diagram for the operation of the start-up circuitof FIG. 7.

[0031]FIG. 10 is an embodiment of a gain amplifier circuit for the boostpower converter of FIG. 5 in accordance with the invention.

[0032]FIG. 11 is an embodiment of a voltage reference circuit for theboost power converter of FIG. 5 in accordance with the invention.

[0033]FIG. 12 is top-level block diagram of an embodiment of thecomparator for the boost power converter of FIG. 5 in accordance withthe invention.

[0034]FIG. 13 is an embodiment of a circuit for the comparator of FIG.12 in accordance with the invention.

[0035]FIG. 14 is an embodiment of a circuit for the timing circuit ofFIG. 5 in accordance with the invention.

[0036]FIG. 15 is an embodiment of a circuit for a current-feedbackoscillator-less controller for the boost power converter of FIG. 2B.

DETAILED DESCRIPTION OF INVENTION

[0037] An explanation of known inductive power converters will behelpful in understanding the invention. Referring to FIG. 2A, atop-level diagram of a known buck power output stage 30 a for a powerconverter 31A is depicted, as an example of a down converter thatprovides an output voltage V_(O) that is less than the input voltageV_(S). The buck output stage 30 a is coupled to an energy source 12 atinput terminals 24, 25 and to a load device 14 at output terminals 26,27 to deliver energy from the energy source to the load device. Theenergy source 12 provides an input voltage V_(S) and an input currenti_(S). The load device 14 receives a current i_(O) and an output voltageV_(O).

[0038] The buck output stage 30 a includes a switch MS, a rectifyingelement MR, an inductive element, such as an inductor L, and acapacitance element, such as a load capacitor C_(L). The load capacitorC_(L) has its positive terminal 32 coupled to the positive outputterminal 26 and its negative terminal 33 coupled the negative outputterminal 27, which is also coupled to the negative input terminal 25forming a ground reference. The load capacitor C_(L), thus, is chargedto the output voltage V_(O). The inductor L has its positive end 34coupled to a feedback voltage node V_(F). The feedback voltage V_(F) isrelated to the voltage V_(L) across the inductor L. The inductor L hasits negative end 35 coupled to the positive output terminal 26.

[0039] The rectifying element MR, implemented as a MOSFET configured asa synchronous rectifier, has its positive terminal (source) 36 coupledto the feedback voltage node V_(F) and its negative terminal (drain) 37coupled the negative input and output terminals, 25, 27. The rectifyingelement MR closes in response to a control signal S1 in order to actlike a diode. The MOSFET of the rectifying element MR has a channel thatconducts current in the reverse direction, and thereby acts like a diodeoften used in oscillator-controlled power converters 20, by having thesource and drain reversed compared to the MOSFET switch MS. The switchMS has its positive end (drain) 38 coupled to the positive inputterminal 24 and its negative end (source) 39 coupled to the feedbackvoltage node V_(F). The switch MS closes in response to control signalS2 turning ON.

[0040] During the discharge state, the control signal S1 is ON to closethe rectifying element MR so that it conducts and the control signal S2is OFF to open the switch MS, allowing the inductor L to discharge intothe load capacitor C_(L). During the charge state, the control signal S1is OFF to open the rectifying element or make it non-conductive MR andthe control signal S2 is ON to close the switch MS, allowing theinductor to be energized by the input current is from the energy source12.

[0041] Referring to FIG. 2B, a boost power output stage 30 b for a powerconverter 31 illustrates a configuration suitable for increasing theoutput voltage V_(O) with respect to the input voltage V_(S). The boostpower output stage 30 b has its input terminals 24, 25, output terminals26, 27, and load capacitor C_(L) configured as described above for thebuck power output stage 30 a. The inductor voltage V_(L) is definedbetween the input terminal 24 and the feedback voltage node V_(F). Thisinductor voltage V_(L) is thus equivalent to the feedback voltage V_(L)minus the input voltage V_(S).

[0042] Rectifying element MR has its negative end 37 coupled to V_(L)?the feedback voltage node V_(F) and its positive end 36 coupled to thepositive output terminal 26. Specifically, a MOSFET is configured as asynchronous rectifier with its drain as the negative end and its sourceas the positive end. MOSFET switch MS has its positive end (drain)coupled to the feedback voltage node V_(F) and its negative end (source)coupled to ground. During the discharge state, the MOSFET switch MSopens in response to control signal S2 turning OFF and rectifyingelement MR closes in response to control signal S1 turning ON, couplingthe energy source 12 and inductor L to the load capacitor C_(L). Thus,the input voltage V_(L) and inductor voltage V_(L) are added in order toboost the output voltage V_(O) imparted to the load capacitor C_(L).During the charge state, MOSFET switch MS closes in response to controlsignal S2 turning ON, coupling the inductor L across the energy source12. Rectifying element MR opens in response to control signal S1 turningOFF, disconnecting the load capacitor C_(L) from the energy source 12and inductor L.

[0043] In accordance with one aspect of the present invention, the buckpower output stage 30 a of FIG. 2A and the boost power output stage 30 bof FIG. 2B are both advantageously efficient and operable with a lowinput voltage (e.g., sub-one volt) by implementation as an integratedcircuit fabricated in a 0.35 micron double salicide process (two metal,two poly salicide) utilizing MOSFET transistor switches capable of lowthreshold (e.g., sub-one volt) control, as described the followingco-pending and commonly owned applications all filed on Mar. 22, 2000:U.S. Ser. No. 09/532,761, entitled “Lateral Asymmetric Lightly DopedDrain MOSFET”, naming Ying Xu et al. (P&G Case No.7992), which is herebyincorporated by reference. In addition to having a low thresholdcontrol, the disclosed MOSFET devices have a low on-resistance, directlycontributing to the efficiency of the power output stage 30 a and 30 bused in accordance with the invention.

[0044] Referring to FIG. 3, a power converter 41 is depicted in blockdiagram form, illustrating oscillatorless, dynamic control of powertransfer from an energy source 12 to a load device 14 coupled to theoutput voltage V_(O) across output terminals 26, 27 in accordance withone aspect of the invention. The power converter 41 is dynamicallycontrolled in that it adapts to the demands from the load device 14,even with variations in the input voltage V_(S), and variation in thetransfer and storage characteristics of the power converter 41.

[0045] The power converter 41 is intrinsically voltage regulated in thatthe amount of energy transferred does not only correspond to the demand,but the rate of energy transfer is controlled so that the output voltageV_(O) remains within an accepted range. This is generally referred to asremaining within an acceptable voltage ripple V_(RIP).

[0046] The power converter 41 includes a power output stage 42 thattransfers the stored energy to the load device 14 and a power controller46 coupled to the power output stage 30 to responsively command theappropriate amount of stored energy to be transferred in accordance withthe present invention.

[0047] In one embodiment, the power output stage 42 is an inductiveDC-DC power converter, of which the above described buck power outputstage 30 a and boost power output stage 30 b are examples. The loadcapacitor C_(L) is electrically coupled across the output terminals 26,27. The load capacitor C_(L) stores electrical charge and provides theoutput voltage V_(O) in relation to its stored charge. The power outputstage 42 also incorporates the inductor L for transferring energy fromthe energy source 12 to the load capacitor C_(L) as discussed above. Theseries resistance for the inductor L and the load capacitor C_(L) mayadvantageously be chosen to be low so that the power converter 41 hasreduced power consumption. The power output stage 42 includes a switchmatrix 48 coupled to the inductor L, load capacitor C_(L), and energysource 12 for configuring the power output stage 30 between a chargestate and a discharge state.

[0048] In addition, the power output stage 30 may be inverting ornoninverting, with respect to whether the output voltage has an oppositealgebraic sign to the input voltage V_(S). For example, a 2.2 V inputvoltage V_(S) may be converted to a −1.6 V output voltage V_(O).Generally, noninverting embodiments are illustrated below for clarity,although one skilled in the art, having the benefit of the instantdisclosure, should recognize application to inverting power converters.

[0049] Multi-loop power controller 46 comprises a dynamic controller 50,a voltage reference 52, and an environmental controller 64 toadvantageously control the power output stage 42. The dynamic controlleris responsive to feedback signals which act as input signals to thecontroller 50. A first control loop 56 is formed by the output voltageV_(O) from output terminal 26 being provided as feedback to the dynamiccontroller 50. The dynamic controller 50 commands the switch matrix 48to transfer additional charge from the energy source 12 to the loadcapacitor C_(L) in response to the output voltage V_(O) being below apredetermined value V_(REF). The dynamic controller 50 makes thedetermination of whether V_(O) is below a predetermined value incomparison to a reference voltage V_(REF) from voltage reference 52. Onesuitable V_(REF) may be provided by the energy source 12 if it issufficiently voltage stable to simplify the voltage reference 52 (e.g.,lithium batteries are voltage stable). Thus, the voltage reference 52may then be provided by a voltage divider or multiplier of the inputvoltage V_(S) to achieve the desired reference voltage V_(REF).

[0050] In addition to the first control loop 56, the multi-loop powercontroller 46 is responsive to a second control loop 58 or input signal.In the second control loop 58, the energy stored in the inductor L issensed indirectly by the dynamic controller 50 as a feedback voltageV_(F), which is the same as or directly related to the inductor voltageV_(L). Alternatively, the energy stored in the inductor L may bedirectly sensed as the strength of an electrical field created byinductor current i_(L), or by a feedback current i_(F), which may be thesame as or directly related to the inductor current i_(L), as will bediscussed with regard to FIG. 15 below. Thus, using the feedback signalassociated with the inductor, any discharge of the inductor L upondemand may be predicated upon the inductor L first reaching an optimumstate of charge (i.e., energy stored in the form of an electricalfield). The optimum state of charge exists because undercharging theinductor L results in unnecessary switching power losses andovercharging the inductor L unnecessarily limits the rate of powertransfer.

[0051] Regarding unnecessary switch power losses, dynamic control of theswitch matrix 48 achieves efficiency in part as described with the firstcontrol loop by remaining in the discharge state until more charge isneeded (i.e., until V_(O) drops below V_(REF)). Prior artoscillator-controlled power converters 20, by contrast, are switched ata fixed rate even when not necessary. Therefore, the present inventionis oscillatorless and provides control non-oscillatorily even though itwill switch periodically, because the switching is determined byfeedback control and does not continuously oscillate at a fixedfrequency.

[0052] Additional efficiency in the dynamic control of the switch matrix48 is realized by remaining in the charge state long enough for theinductor L to acquire a significant amount of charge. For example,charging to 40% rather than 80% of full charge would require that theoperating frequency would double to transfer the same power. The switchMS and rectifying element MR dissipate power in relation to thisincreased operating frequency. This is due to low-on resistance andhigh-off resistance of the Field Effect Transistors used. Since powerconsumption is a function of the square of the current times theresistance, most of the power loss occurs during the transition.Consequently, the second control loop 58 senses the voltage level acrossthe inductor L to avoid undercharging during the charge state, and thusavoid unnecessary switching losses.

[0053] Optimizing the charge on the inductor L in accordance with oneaspect of the invention also includes avoiding overcharging. Inductorsare characterized by their rate of charging as a function of time.Specifically, as inductors approach a filly energized condition, theirrate for accepting additional energy decreases. Thus, the initial amountof energy acquired by the inductor takes less time than a later similaramount of energy. For example, it would take less time to energize theinductor L twice to 45% than to energize the inductor L once to 90%,even though the same amount of energy would be accepted by the inductorL. Consequently, leaving the switch matrix 48 in the charge state for aperiod of time longer than required to achieve the optimum level ofcharge of the inductor L misses an opportunity to transfer more power.

[0054] It should be appreciated that the optimum level of stored energyfor a particular inductive component may be determined empiricallyand/or analytically as would be apparent to those skilled in the arthaving the benefit of the instant disclosure.

[0055] In combination with one or more other control loops 56, 58discussed above, the power converter 41 may advantageously include aforward control loop 60 as an input signal whereby one or moreparameters of the energy source 12 are provided to the dynamiccontroller 50. One use of the forward control loop 60 would includedisabling (i.e., interrupting output current to the output terminals 26,27) and/or bypassing (i.e., directly coupling the energy source 12 tothe output terminals 26, 27) the power converter 31 due to unsafeconditions or performance limiting conditions sensed in the energysource 12. For example, a low input voltage may indicate inadequateremaining charge in the energy source 12 to warrant continued operationof the power converter 31. As another example, the electrical currentdrawn from the energy source 12 may be too high for sustained operation.Thus, a protection circuit may be included in the power converter 41 forinterrupting output current to the output terminals 26, 27 based uponcontrol loop 60.

[0056] As yet an additional example of dynamic control, a large demandby the load device 14 may warrant continued operation of the powerconverter 41 in parallel to a direct coupling of the energy source 12 tothe output terminals 26, 27. This may be especially true when the inputvoltage V_(S) and desired output voltage V_(O) are approximately thesame. An increased output current capacity is achievable by having twopaths providing current to output terminals 26, 27.

[0057] As a further example, the feedback voltage V_(F) (second controlloop 58), and the input voltage V_(S) (forward control loop 60) mayindicate that the power converter 41 is fully discharged and is in astart-up condition. This start-up condition may advantageously warrantuse of a rapid progressive start-up circuit, an example being describedbelow in accordance with one aspect of the invention.

[0058] In combination with one of the other control loops or controlinput signals 56, 58, and 60, the power controller 46 may furtherinclude an adaptive control loop 62, as represented by an environmentalcontroller 64. The environmental controller 64 senses a controlparameter 66 and provides a command 68 to the dynamic controller 50 foraltering the predetermined value for the output voltage V_(O). Forexample, the environmental controller 64 may sense that the dynamiccontroller 50 has become unstable, and in response thereto, may providea signal to drive the dynamic controller 50 to a stable outputcondition. More particularly, the environmental controller 64 may beadapted to sense an unstable operating condition of the power converter41, such as the instantaneous output voltage and current eachapproaching a constant value. The environmental controller 64 may thenadjust the predetermined value to drive the power converter 41 to astable operating condition. Moreover, such altering of the predeterminedvalue may include resetting of the dynamic controller 50 to a stableinitial condition.

[0059] As another example, the adaptive control loop 62 may include acontrol signal S_(C) that is input to the environmental controller 64whereby the dynamic controller 50 can be made to respond to changes in aload device 14 (e.g., CPU, volatile memory, analog-to-digital converter,digital-to-analog converter) or to other parameters. The load device 14may advantageously perform better with an adjusted output voltage V_(O)from the power converter 41. As another example, the output controlsignal S_(C) may be a reconfiguration control signal, such as forselecting a desired inverting or noninverting mode or predeterminedoutput voltage V_(O). As yet another example, a protective function(e.g., bypassing, disabling, or altering the output voltages) may bedictated by the S_(C) command to preclude damaging a load device 14. Forexample, the load device 14 may fail under high current, and thus,limits may be imposed to preclude this occurrence.

[0060] Depending upon the type of switch matrix 48 that is utilized inthe invention, various control signals are generated by the dynamiccontroller 50 for the switch matrix 48, as represented by switch signalsS1, S2, S3 to SN. For example, control signals S3 to SN may representinputs for a configuring the power output stage 42 to variouscombination in order to provide a step up, step down, inverted, and/ornoninverted output arrangement.

[0061] It should be appreciated that the inductor L and the loadcapacitor C_(L) are illustrative of charge storage and transfercomponents and may represent discrete elements or integrated circuitelements.

[0062] Moreover, due to the flexibility of the dynamic controller 50,the load capacitor C_(L) may include various levels of storagecapability, such as with small capacitors (e.g., ceramic, chip thickfilm, tantalum, polymer) and large capacitors (e.g., ultra-capacitors,pseudo-capacitors, double-layer capacitors). The amount of inductanceand capacitance is reflective of the amount of storage capability. Thus,providing the same amount of energy transfer requires either that smalldoses of energy be transferred from a small inductor L with a highoperating frequency or that larger doses of charge be transferred moreslowly. Thus, the power converter 41 is flexible in that the samedynamic controller 50 may control various power output stages 42. Inparticular, unlike the prior art oscillator-controlled power converter20, the dynamic controller 50 may operate in the low operating frequencyrange appropriate for power output stages 30 incorporatingultra-capacitors.

[0063] It should further be appreciated that the energy source 12 mayinclude various electrical charge storage or generating devices such asone or more electrochemical cells (e.g., a battery), photovoltaic cells,a direct-current (DC) generator (e.g., a wrist watch charged by amotion-powered generator in combination with a rechargeable battery),and other applicable power sources.

[0064] As another example, power converters 41 consistent with theinvention may be used advantageously in electronic devices powered byother power supplies. For example, a device receiving its power from astandard alternating current (AC) wall plug generally transforms the ACpower into direct current (DC) power for electronic portions of thedevice. The DC power provided may be unsuitable for all or portions ofthe electronics without further adjustment and regulation. For example,a microprocessor may be operating at 2.2 V whereas input/outputelectronics may operate at 5 V. Consequently, a power converter 41 inaccordance with the invention may be used to step-down the input voltageto the microprocessor.

[0065] Referring to FIG. 4, one embodiment of a circuit for a start-stopcontroller 50 a for the power output stage 30 b of FIG. 2B isillustrated. Generally known power converters 20, including inductivepower converters, continue to oscillate, even when the demand from theload device 14 makes the power converter inefficient. Consequently, thestart-stop controller advantageously stops the oscillation of a PulseWidth Modulation (PWM) output when the load capacitor C_(L) isadequately charged.

[0066] Specifically, the boost power output stage 30 b is as describedabove in FIG. 2B, except for the addition of a capacitive element C1coupled across input terminals 24, 25 which is used to enhance thestability of input voltage V_(S).

[0067] The start-stop controller 50 a is responsive to input signals forpulse width modulation (PWM), and oscillated control of the power outputstage 30 b by selectively generating the control signal S1 to close therectifying element MR during the discharge state and to open therectifying element MR during the charge state, and selectivelygenerating the control signal S2 to open the switch MS during thedischarge state and to close the switch MS during the charge state. Thestart-stop controller 50 a senses a low demand as indicated by thecomparison of the reference voltage V_(REF) and the output voltage V_(O)to hysteretically stop the oscillated control signal so that the outputstage 30 b remains in the discharge state. The start-stop controller 50a includes a hysteretic comparator 70 responsive to the referencevoltage V_(REF), the output voltage V_(O) and the feedback voltage V_(F)to generate a duty-cycle signal, and hysteretically responsive to theoutput voltage V_(O) and the reference voltage V_(REF) to generate astop signal. A modulator 72 generates an oscillation signal having thepredetermined frequency. An SR flip flop 74 is set by the set duty-cyclesignal and reset by the oscillation signal to produce a switching signalwhich determines the charge state and the discharge state. A multiplexer75 is responsive to the switching signal to generate the control signalsS1 and S2. The multiplexer 75 has a predetermined state switching delayto mitigate cross conduction of the power output stage 30 b. Themultiplexer 75 is also responsive to the stop signal to stoposcillations until more energy is needed by turning OFF control signalS2 to open switch MS and by turning ON control signal S1 to closerectifying element MR.

[0068] In addition, a start-up circuit 76 biases the start-stopcontroller 50 a when the power output stage 30 b is discharged, as wellas providing initial charge to the load capacitor C_(L).

[0069] Referring to FIG. 5, an embodiment of a circuit for avoltage-feedback dynamic controller 50 b is shown as used for a boostpower converter such as shown in FIG. 2B. In particular, the firstcontrol loop 56 provides the output voltage V_(O) and the second controlloop 58 provides the feedback voltage V_(F) to the dynamic controller 50b, which provides control of the charge/discharge states of theconverter with control signals S1 and S2.

[0070] The start-up circuit 76 is powered by the input voltage V_(S)from the input terminal 24. The start-up circuit 76 responds to thefeedback voltage V_(F) such that when the power output stage 30 b isfully discharged and thus the controller 50 b is not yet operating, thestart-up circuit 76 provides a bias to the voltage reference 52, to again amplifier 78 and to the dynamic controller 50 b.

[0071] The gain amplifier 78 receives the output voltage V_(O) and thefeedback voltage V_(F) respectively from the first and second controlloops 56, 58, and provides a desired bias and gain to each to produce afiltered and amplified output voltage V′_(O) and feedback voltageV′_(F). The desired bias and gain may be selected for appropriateresponsiveness and stability of the dynamic controller 50 b.

[0072] The dynamic controller 50 b receives as input signals the inputvoltage V_(S), the reference voltage V_(REF) from the voltage reference52, the filtered feedback voltage V′_(F), and the filtered outputvoltage V_(′) _(O). More particularly, during the discharge state, thedynamic controller 50 b couples the reference voltage V_(REF) to apositive comparator input 80 via a switch M2 responsive to a controlsignal S1′. The dynamic controller 50 b couples the filtered outputvoltage V′_(O) to a negative comparator input 81 via a switch M4responsive to the control signal S1′. During the charge state, thedynamic controller 50 b couples the input voltage input voltage V_(S) tothe positive comparator input 80 via a switch M1 responsive to a controlsignal S2′. The dynamic controller 50 b further couples the filteredfeedback voltage V′_(F) to the negative comparator input 81 via a switchM3 responsive to the control signal S2′.

[0073] The dynamic controller includes a comparator 82 for generating acomparison signal based on the input to the positive and negativecomparator inputs 80, 81, as described in FIG. 6 below. The comparisonsignal is used by a timing circuit 84 to produce the control signals S1,S2, S1′, S2′, S1N and S2N, as described below in FIG. 14. Control signalS1 is used to control the rectifying element MR, and has sufficientcurrent to control a power MOSFET. Control signal S2 is used to controlthe switch MS, and has sufficient current to control a power MOSFET. S1′and S2′ are unamplified versions of control signals S1, S2, used withinthe dynamic controller 50 b. Control signals S1N and S2N are invertedversions respectively of control signals S1, S2, used for controllingthe start-up circuit 76.

[0074] Referring to FIG. 6, a flow diagram for an operation 100 of thevoltage-feedback dynamic controller 50 b of FIG. 5 is shown. Theoperation 100 begins with the controller not operating, and thus controlsignals S1 and S2 are OFF (block 102). Thus a start-up operation 104 isperformed, as described below in more detail with respect to FIGS. 7-9.Then operation 100 begins dynamic operation, alternating as requiredbetween charge and discharge states.

[0075] Then, a determination is made as to whether the output voltageV_(O) is less than the reference voltage V_(REF) (block 106). If not,then the load capacitor C_(L) is sufficiently charged and operation 100repeats block 106, remaining in the discharge state.

[0076] However, if in block 106 the output voltage V_(O) is less thanthe reference voltage V_(REF), then a start-up delay is performed (block108). Then, control signal S1 is turned OFF, opening rectifying elementMR (block 110). A cross conduction delay occurs thereafter with controlsignal S2 already OFF and switch MS is open (block 112). This preventsinefficient shorting of the power output stage 30 b. Then, controlsignal S2 is turned ON, closing the switch MS, beginning the chargestate (block 114).

[0077] At block 116, a determination is made as to whether the inductorL is sufficiently energized by determining whether the feedback voltageV_(F) is greater than or equal to a predetermined fraction β of theinput voltage V_(S), where 0<β<1, with block 116 repeating untilsatisfied.

[0078] The fraction β is chosen either analytically or empirically forproviding an optimum energy transfer amount. A relatively small fractionβ results in a higher operating frequency of switching. Since typicalswitches dissipate energy mostly during the transition from OFF to ONand from ON to OFF, minimizing switching increases efficiency. However,a relatively high fraction β limits the capacity of the power outputstage 30 b since the inductor L has a diminishing rate of energy storageas it approaches a fully energized state.

[0079] When block 116 is satisfied, then a start-up delay is performed(block 118). Then, the control signal S2 is turned OFF, opening theswitch MS (block 120). A cross conduction delay occurs thereafter withcontrol signal S2 already OFF and switch MS now open (block 122). Thencontrol signal S1 is turned ON, closing the rectifying element MR,beginning the discharge state. Operation 100, thus returns to block 106to repeat the sequence.

[0080]FIG. 7 is an embodiment of a start-up circuit 76 for the boostpower converter of FIG. 5.

[0081]FIG. 8 is a wave diagram for the start-up circuit 76 of FIG. 7.

[0082] Referring to FIG. 9, the operation 104 of the start-up circuit 76of FIG. 7 is illustrated. The start-up operation 104 begins with aninitial condition in block 150 that a load is already applied to thepower converter and in block 152 that an input voltage is available tothe power converter. Then a determination is made as to whether thepower controller is off and not controlling the power output stage(block 154). If the power controller is on (block 154), then a smallstart-up capacitor C_(QPUMP) is floated (block 156) and the start-upoperation 104 is complete.

[0083] It should be appreciated that the controller 50 b is off withrespect to the start-up operation 104 even after the controller beginsto operate. That is, control signals to the start-up circuit 76generally becomes available before the controller actually has developeda sufficient voltage to operate the rectifying element MR and the switchMS.

[0084] If in block 154 the controller is off, then a start-up switch isclosed to provide input voltage V_(S) to the start-up capacitorC_(QPUMP) (block 158) and the start-up capacitor C_(QPUMP) is referencedto ground (block 160). When the start-up capacitor C_(QPUMP) is charged(block 162), it is first used to bias the controller (block 164), andthen discharged into the load capacitor (block 166) and the start-upcircuit including start-up capacitor C_(QPUMP) is uncoupled from thepower output stage of the power converter (block 168). Then, thestart-up operation 104 returns to block 154 to see if this start-upcycle was sufficient to activate the controller and subsequent start-upoperation cycles repeated as necessary.

[0085] Referring to FIG. 10, an embodiment of the gain amplifier circuit78 for the dynamic controller 50 b of FIG. 5 is depicted. The gainamplifier circuit 78 accepts as input signals the feedback voltage V_(F)and the output voltage V_(O). An operational amplifier 180 is biased bythe start-up circuit 76. The positive input of the operational amplifier180 is the input which is coupled through voltage divider R3/R4. Thenegative input and output of the operational amplifier are coupled forfeedback through resistors R1 and R2. The resistors may be integrated(e.g., poly resistors) and of high impedance (e.g., mega-ohm range) forlow power consumption.

[0086] Referring to FIG. 11, one embodiment of a voltage referencecircuit 52 is shown for the boost power converter 30 b of FIG. 5,capable of sub-one volt input voltage V_(S) operation in accordance withan aspect of the invention. A constant current circuit 200 powers avoltage reference-to-rail circuit 202, isolating the voltagereference-to-rail circuit 202 from changes in the input voltage V_(S).An output buffer 204 amplifies an unamplified reference voltage from thevoltage reference-to-rail circuit 202. In order to temperaturecompensate the voltage reference-to-rail circuit 202, a parallel diodearray Proportional to the Absolute Temperature (PTAT) circuit 206 biasesthe circuit 202.

[0087] Referring to FIGS. 12 and 13, one embodiment of a comparator 82is depicted for the boost power converter 30 b of FIG. 5. Differentialamplifiers 206-210 are advantageously used since they are effective inrejecting common-mode signals. For example, common-mode signals may beinduced noise on the inputs. Integrated circuit differential amplifiershave relatively low output gain. This has implications in two ways:non-linearity in an input transistor and in providing necessary currentgain for the timing circuit 84.

[0088] For providing some cancellation of input non-linearity, a threedifferential amplifier combination is depicted, wherein the firstdifferential amplifier 206 receives a V+ input at its negative input andV− at its positive input. A second differential amplifier 208 receivesV− at its negative terminal and V+ at its positive terminal. The outputof the first differential amplifier 206 is coupled to a negativeterminal of a third differential amplifier 210 and the output of thesecond differential amplifier 208 is coupled to a positive input of thethird differential amplifier 210. A fourth differential amplifier 212 isconfigured as a voltage follower buffer to increase the current of acomparator switching signal (Out+, Out−) from the third differentialamplifier 210.

[0089] Referring to FIG. 14, one embodiment of the timing circuit 84 isdepicted for the power controller 46A of FIG. 5.

[0090] Referring to FIG. 15, an embodiment of a circuit for acurrent-feedback oscillator-less dynamic controller 50 b is shown forthe boost power output stage 30 b of FIG. 2B. Specifically, a feedbackcurrent i_(F) sensed by a current probe 300 at feedback voltage V_(F)node. The feedback current i_(F) is related to, or the same as, theinductor current i_(L). The sensed feedback current i_(F) is convertedinto a feedback voltage V_(F) by a current converter 302 for an input tothe gain amplifier 78 as described above.

[0091] While the present invention has been illustrated by descriptionof several embodiments and while the illustrative embodiments have beendescribed in considerable detail, it is not the intention of applicantsto restrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications readily appear to thoseskilled in the art.

[0092] For example, for clarity, the switch MS and rectifying element MRare normally open, closed by a positive ON signal. It would be apparentto those skilled in the art having the benefit of the instant disclosureto use normally closed switches and/or switches closed by a negative ONsignal.

[0093] As another example, a power converter consistent with theinvention may be incorporated in a wide range of products. For example,a power converter 31 taking advantage of the small size and low powerconsumption (i.e., efficiency) properties described above mayadvantageously be incorporated into a battery package to enhance batteryservice life and energy and amplitude on demand. Incorporating the powerconverter would be accomplished in manner similar to that disclosed inthe following co-pending and commonly owned applications all filed onApr. 2, 1998: U.S. Ser. No. 09/054,192, entitled PRIMARY BATTERY HAVINGA BUILT-IN CONTROLLER TO EXTEND BATTERY RUN TIME, naming VladimirGartstein and Dragan D. Nebrigic; U.S. Ser. No. 09/054,191, entitledBATTERY HAVING A BUILT-IN CONTROLLER TO EXTEND BATTERY SERVICE RUN TIMEnaming Vladimir Gartstein and Dragan D. Nebrigic; U.S. Ser. No.09/054,087, ENTITLED BATTERY HAVING A BUILT-IN CONTROLLER, namingVladimir Gartstein and Dragan D. Nebrigic; and U.S. ProvisionalApplication Serial No. 60/080,427, entitled BATTERY HAVING A BUILT-INCONTROLLER TO EXTEND BATTERY SERVICE RUN TIME, naming Dragan D. Nebrigicand Vladimir Gartstein. All of the aforementioned applications arehereby incorporated by reference in their entirety.

What is claimed is:
 1. A power converter with input terminals forcoupling to an energy source and output terminals for coupling to a loaddevice, the power converter characterized by: an output stage forselectively coupling the input terminals to the output terminals todeliver energy from an energy source to a load device; a controlleroperably coupled to the output stage for dynamically controlling saidselective coupling of the input and output terminals; the output stagefurther characterized by an inductive element coupled to the inputterminals, a capacitive element coupled to the output terminals, arectifying element closingly responsive to a first state and openlyresponsive to a second state, and a switch responsive to a controlsignal S2 from the controller, the rectifying element and the switchbeing operably coupled with respect to said inductive and capacitiveelements for causing the inductive element to be coupled to thecapacitive element to discharge energy therefrom into the capacitiveelement during the first state and causing the inductive element to beenergized during the second state; the controller being responsive toinput signals for selectively and non-oscillatorily generating thecontrol signal S2 to open the switch in said first state and close theswitch in said second state, the input signals to the controllerincluding one or more of an output voltage across the output terminals,an input voltage across the input terminals, a selectable referencevoltage and a feedback signal measured with respect to the inductiveelement.
 2. The power converter of claim 1, further characterized byincluding an amplifier coupled to the output stage and the controller,the amplifier configured to amplify at least one of the feedback voltageand the output voltage.
 3. The power converter as in any of the previousclaims, characterized in that the controller includes a switch driveroperable for amplifying the control signal S2 to the switch.
 4. Thepower converter as in any of the previous claims, characterized in thatthe rectifying element is further characterized by a Field EffectTransistor.
 5. The power converter as in any of the previous claims,characterized in that the switch is further characterized by at leastone low threshold, low on-resistance MOSFET.
 6. The power converter asin any of the previous claims, characterized in that the controller isfurther characterized by a voltage reference circuit for producing thereference voltage.
 7. The power converter as in ay of the previousclaims, further characterized in that the controller includes acomparator for responding to the input signals, the comparator includinga first and second comparator input coupled respectively to two of theinput signals, the comparator generating a switching signal at acomparator output to define the first and second states.
 8. The powerconverter as in any of the previous claims, further characterized by acapacitive element electrically coupled across the input terminals forinput voltage stability.
 9. The power converter as in any of theprevious claims, further characterized in that the inductive elementincludes an inductive element current, the controller further comprisinga current converter coupled to the inductive element, operable to sensethe inductive element current and to convert the inductive elementcurrent into the feedback voltage.
 10. An integrated circuit including apower converter with input terminals for coupling to an energy sourceand output terminals for coupling to a load device, the integratedcircuit characterized by: an output stage for selectively coupling theinput terminals to the output terminals to deliver energy from an energysource to a load device; a controller operably coupled to the outputstage for dynamically controlling said selective coupling of the inputand output terminals; the output stage adapted for coupling an inductiveelement to the input terminals and for coupling a capacitive element tothe output terminals, the output stage further characterized by arectifying element responsive to a control signal S1, and a switchresponsive to a control signal S2 from the controller, the rectifyingelement and the switch being operably coupled with respect to saidinductive and capacitive elements for causing the inductive element tobe coupled to the capacitive element to discharge energy therefrom intothe capacitive element during a first state and causing the inductiveelement to be charged during a second state; the controller beingresponsive to input signals for selectively and non-oscillatorilygenerating the control signal S1 to close the rectifying element duringthe first state and to open the rectifying element during the secondstate, and generating the control signal S2 to open the switch duringthe first state and to close the switch during the second state, theinput signals to the controller including one or more of an outputvoltage across the output terminals, an input voltage across the inputterminals, a selectable reference voltage and a feedback voltagemeasured across the inductive element.